Trace amounts of metals and other contaminants may be found in effluent streams from many industrial processes. Recovery of these metals and other elements from the effluent stream is an economic concern—both in reclaiming the metals and as a means of cleaning effluent streams to avoid pollution and to comply with environmental regulations. Regulations are expected to require removal of many metals to part per billion (ppb) levels. There is a need for a system that is capable of removing metals from an effluent stream in an effective and efficient manner.
It is known that poly(dithiocarbamate) (PDTC) resins are effective as chelated ion exchangers for the separation and concentration of metals and other compounds. It has been shown that more than 50 elements complex with a PDTC resin. Mlyazaki, A. and Barnes, R. “Complexation of Some Transition metals, rare Earth Elements, and Thorium with a Poly(dithiocarbamate) Chelating Resin”, Anal. Chemistry, vol. 53, (1981), pp. 299–304.
U.S. Pat. No. 4,518,760 describes the preparation of a polydithiocarbamate resin useful in removing heavy metals and other ions from aqueous solutions. U.S. Pat. No. 4,578,195 describes a process for purifying effluents and purge streams containing trace element, using a polydithiocarbamate resin having a sulfur content of from 6 to 7 percent.
One problem with the PDTC resins of the prior art is that the amount of effluent that can be passed though the resin, and still achieve acceptable removal of cationic contaminants, is unacceptably low for use in many industrial processes.
Surprisingly it has been found that polydithiocarbamate resins made by a novel process, and PDTC composites, are capable of handling high throughputs of effluent, while removing metals to desired parts per billion (ppb) levels.